Bidirectional non-innocence of the β-diketonato ligand 9-oxidophenalenone (L−) in [Ru([9]aneS3)(L)(dmso)]n, [9]aneS3 = 1,4,7-trithiacyclononane

Abstract

The new compound [Ru^II([9]aneS3)(L)(dmso)]ClO₄ ([1]ClO₄) ([9]aneS3 = 1,4,7-trithiacyclononane, HL = 9-hydroxyphenalenone, dmso = dimethylsulfoxide) has been structurally characterised to reveal almost equal C–O bond distances of coordinated L⁻, suggesting a delocalised bonding situation of the β-diketonato ligand. The dmso ligand is coordinated via the sulfur atom in the native (1⁺) and reduced states (1 and 1⁻) as has been revealed by X-ray crystallography and by DFT calculations. Cyclic voltammetry of 1⁺ exhibits two close-lying one-electron oxidation waves at 0.77 V and 0.94 V, and two similarly close one-electron reduction processes at −1.43 V and −1.56 V versus SCE in CH₂Cl₂. The electronic structures of 1ⁿ in the accessible redox states have been analysed via experiments (EPR and UV-vis-NIR spectroelectrochemistry) and by DFT/TD-DFT calculations, revealing the potential for bidirectional non-innocent behaviour of coordinated L˙^/−/˙²⁻. Specifically, the studies establish significant involvement of L based frontier orbitals in both the oxidation and reduction processes: [([9]aneS3)(dmso)Ru^III–L˙]³⁺ (1³⁺) ⇌ [([9]aneS3)(dmso)Ru^III–L⁻]²⁺/[([9]aneS3)(dmso)Ru^II–L˙]²⁺ (1²⁺) ⇌ [([9]aneS3)(dmso)Ru^II–L⁻]⁺ (1⁺) ⇌ [([9]aneS3)(dmso)Ru^II–L˙²⁻] (1) ⇌ [([9]aneS3)(dmso)Ru^II–L³⁻]⁻/[([9]aneS3)(dmso)Ru^I–L˙²⁻]⁻ (1⁻).